The present invention relates to a negative pressure air bearing slider intended to be employed in an information storage device such as a magnetic disk drive.
Air bearing sliders are often employed in magnetic disk drives. The air bearing slider allows a transducer element to fly above the disk surface of a magnetic disk when information is read or written from or onto the magnetic disk. Alternatively, the slider may be positioned below the magnetic disk, in which case the slider flies a slight distance below the lower disk surface. Either way, an air bearing surface (ABS) is defined on the surface of the slider body that opposes the disk surface. When the storage disk rotates, an air stream generated along the disk surface acts upon the air bearing surface to separate the slider body a slight distance from the disk surface. For the sake of simplicity, throughout this specification, this separation will be referred to as the flying height, regardless of whether the slider is above the disk or below the disk.
Recently, higher and higher storage densities are being expected in the field of magnetic disk drives. In order to achieve a higher storage density, it is beneficial to reduce the flying height of the slider body. However, as the flying height is reduced, the slider body tends to collide with the disk surface during flying.
Some prior art devices include a negative pressure air bearing slider that is capable of generating negative pressure that opposes the lift (or positive pressure) acting upon the air bearing surface. The balance between the negative pressure and the lift serves to restrict the flying height in this type of negative pressure air bearing slider. The negative pressure serves to draw the slider body toward the disk surface so that it is possible to stabilize the flying behavior of the slider body. As a result, the probability of collisions between the slider body and the disk surface can be reduced.
The growing demand for higher storage densities requires further improvements in the stability of the slider body, and at the same time also requires an increased resistance to any rolling action of the slider body. If sufficient resistance to rolling is not present, the slider body tends to roll around its center axis along the air stream during flying, and the slider body may collide with the disk surface.
It is accordingly an object of the present invention to provide a negative pressure air bearing slider with both increased stability and an increased resistance to rolling during flying.
According to a first aspect of the present invention, there is provided a negative pressure air bearing slider that includes a first air bearing surface formed oil a bottom of a slider body at an upstream position so as to extend in a lateral direction of the slider body; and a pair of second air bearing surfaces formed on the bottom of the slider body separately from the first air bearing surface at downstream positions that are spaced apart in the lateral direction so as to define an air stream passage therebetween.
With the aforementioned slider, the second air bearing surfaces that are spaced apart in the lateral direction serve to generate the lift or positive pressure at the downstream position at which a transducer or head element is in general embedded in the slider body. Since a pair of spaced lifts support the slider body at the downstream position, it is possible to remarkably enhance the slider body""s stiffness to rolling action.
The first air bearing surface may be defined on the lower surface of a front rail that extends from the bottom of the slider body near an upstream end thereof. The front rail also extends in the lateral direction of the slider body. The front rail foremost receives the air stream along the disk surface, so that the negative pressure generated behind the front rail cannot be reduced. In addition, the second air bearing surfaces may be respectively defined on lower surfaces of a pair of rear rails that extend from the bottom of the slider body at the downstream positions. These rear rails are spaced in the lateral direction so as to define the air stream passage therebetween.
The first and second air bearing surfaces are preferably connected to the lower surfaces of the front and rear rails via steps. The steps serve to generate a higher positive pressure at the first and second air bearing surfaces.
The negative pressure air bearing slider preferably includes a pair of side rails that are formed on the bottom of the slider body so as to extend downstream from the lateral ends of the front rail. The side rails serve to prevent the air stream that flows around the lateral ends of the front rail from entering the space behind the front rail. Accordingly, it is possible to reliably generate a higher negative pressure behind the front rail. In particular, the side rails preferably have a thickness that is smaller than that of the rear rails in the lateral direction. The thinner side rails serve to enlarge a negative pressure cavity surrounded by the side rails behind the front rail, so that the negative pressure can be increased.
Moreover, a groove is preferably formed in the side rail so as to draw air running around the front rail into the air stream passage. The groove serves to avoid saturation of the negative pressure at lower tangential velocities of the storage disk, even if lower front and rear rails are employed. As a result, the groove enables the negative pressure to reliably follow increases of the tangential velocity, so that the negative pressure air bearing slider may keep the flying height of the slider body constant, irrespective of variations in the tangential velocity.
In addition, a pad may be formed on the lower surface of the front or rear rail so as to prevent the first or second air bearing surface from sticking to the disk surface of a storage disk when the slider body is seated upon the disk surface. Such pads serve to avoid the first or second air bearing surface from directly contacting the disk surface. As a result, less adhesion of a lubricating agent or oil spread over the disk surface acts on the slider body, so that the slider body can immediately take off from the disk surface at the beginning of rotation of the storage disk.
Further, the second air bearing surface in which a transducer element is embedded may have a surface area that is smaller than that of the other second air bearing surface. The smaller second air bearing surface with a transducer element serves to keep the slider body in a slanted attitude by a roll angle. Accordingly, it is possible to minimize the distance between the bottom of the slider body and the disk surface around the transducer element.
When the second air bearing surface with the transducer element is intended to be smaller than the other air bearing surface, the second air bearing surface with the transducer element may have an upstream end extending by a first width in the lateral direction so as to lead to the step, and a downstream end extending by a second width that is larger than the first width in the lateral direction. For example, in the case where the transducer element comprises a magnetoresistance (MR) element, the MR element should be protected between a pair of shield layers. If the shield layers fail to have a lateral size that is large enough to shield the MR element from magnetic interference of the vicinal magnetic field, the MR element will not be able to correctly read data. In general, the slider body is kept in a slanted attitude to bring the downstream end closer to the disk surface. As long as the slanted attitude is kept, the transducer element embedded in the slider body at the downstream position can approach the disk surface. Accordingly, the wider downstream end enables the second air bearing surface to be of a smaller area, while still keeping the larger lateral size of the shield layers at the same time.
In addition, when the second air bearing surface with the transducer element is intended to be smaller than the other air bearing surface, an upstream end extending in the lateral direction so as to define the step in front of the second air bearing surface with the transducer element may be disposed more downstream than an upstream end extending in the lateral direction so as to define the step in front of the other second air bearing surface. Such disposition of the second air bearing surfaces serves to reduce the length of the second air bearing surface with the transducer element in the direction of air stream as compared with that of the other second air bearing surface. Accordingly, the smaller second air bearing surface can be realized to set the lift at the second air bearing surface with the transducer element that is smaller than that of the other second bearing surface. It is therefore possible to reduce the lift at the second air bearing surface with the transducer element without a reduction in the lateral width of the shield layers.
When the upstream end of the second air bearing surface with the transducer is displaced downstream as described above, it is preferable to adjust the size of the groove between the rear and side rails. For example, if the side rail fails to extend toward the rear rail to follow the displacement of the upstream end of the second air bearing surface, the groove becomes larger or wider. The wider groove may release the negative pressure generated behind the front rail. On the other hand, when the side rail is extended to follow the displacement of the upstream end, a smaller or narrower groove can be obtained, so that a higher negative pressure can be maintained behind the front rail. A higher negative pressure enables the second air bearing surface with the transducer element to reliably approach the disk surface as closely as possible.
Furthermore, when the lift at the second air bearing surface with the transducer element needs to be reduced, for example, the position of the second air bearing surface can be determined relative to the lower surface of the rear rail. The aforementioned higher positive pressure generated at the steps depends upon not only its areas and heights, in addition to the area of the second air bearing surfaces, but also upon the extent of the lower surfaces leading to the steps on the rear rails. Smaller lower surfaces make less positive pressure, while larger surfaces make larger positive pressure. Accordingly, if the lateral width of the lower surface leading to the step facing outward of the slider body on the rear rail is reduced, the lift can be reduced at the second air bearing surface with the transducer element, since the step facing outward of the slider body tends to receive a larger amount of air stream than the step facing inward of the slider body.
Furthermore, when the lift at the second air bearing surface with the transducer element needs to be reduced, for example, the second air bearing surface with the transducer element may include a downstream end extending in the lateral direction at the downstream position and displaced upstream. The aforementioned negative pressure air bearing slider has the maximum positive pressure at the downstream end of the slider body. Accordingly, when the downstream end is displaced upstream so as to reduce the area of the second air bearing surface with the transducer element, the lift can be efficiently reduced at the second air bearing surface with the transducer element.
It should be noted that the negative pressure air bearing slider of the present invention may be employed in storage disk drives such as a hard disk drive unit (HDD).